1. Field of the Invention
The present invention relates generally to a robotic system that is useful in nuclear power plants and other structures with a difficult to access geometry. More particularly, it relates to such a system which is capable of locating and removing foreign objects that have been accidentally introduced into such structures with a difficult to access geometry, such as in the tube bundles of a nuclear power plant s steam generators.
2. Description of the Prior Art
Nuclear power generation equipment consists of two major parts, the reactor and the steam generator. The steam generator includes a heat exchanger, which, in simple terms, consists of a bundle of thin wall tubes, which are tightly spaced and arranged in a matrix-like fashion. The spacing between the tubes is less than 0.5 inches, and the tube height extends to several feet. Hot reactor coolant is pumped through the tubes, which in turn heats water under pressure above the boiling point to several hundred degrees, thus generating steam.
During reactor shut down for refueling or any other reason, repair and maintenance technicians enter various areas, one of which is the steam generator housing. During such entry, accidental dropping of such items as welding rods, washers, screws and the like is possible. Such items can cause damage to the thin wall tubes if they are not retrieved. Repairing, replacing or plugging such damaged tubes is very expensive, both in terms of the labor involved and required reactor shut down. To date, it has not been possible to retrieve such items, due to the physical constraints of the steam generator geometry and the presence of radiation.
U.S. Pat. No. 4,638,667, issued Jan. 27, 1987 to Zimmer et al. discloses a remote probe positioning apparatus including a flexible tape which has an optical fiber cable running the length of the tape and a retractor tool at a distal end of the tape. However, no details are given on the construction and operation of the retractor tool. Further development is therefore required in order to provide a system for removing foreign objects which will meet the needs of nuclear power plant steam generator geometry and similar difficult to access geometries.